1. Field of the Invention
Apparatuses and methods consistent with exemplary embodiments relate to an image forming apparatus and an image forming method thereof, a host apparatus and an image-forming control method thereof, an image forming method of an image forming system, and more particularly, to an image forming apparatus and an image forming method thereof, a host apparatus and an image-forming control method thereof, an image forming method of an image forming system, which control an image density in a system using a graphic device interface (GDI) type image forming apparatus.
2. Description of the Related Art
In general, an image forming apparatus is an apparatus which prints printing data generated in a terminal apparatus, such as a computer, onto a recording medium, such as paper. As an example of the image forming apparatuses, there are copiers, printers, facsimiles, multiple function peripherals (MFPs) configured to implement multiple functions thereof through one apparatus.
Recently, laser image forming apparatuses have been gradually increasing in use, as they have remarkably superior effects in terms of print quality, print speed, noise in printing, and the like as compared with dot image forming apparatuses or inkjet image forming apparatuses which are currently mainly used. The laser image forming apparatuses denote an image forming apparatus using the principle of sequentially coating toner on an organic photo conductor (OPC) using a laser beam modulated into a picture signal, transferring the toner coated on a surface of the OPC onto a printing paper, and fusing the toner on the printing paper with high temperature and pressure.
In particular, in recent years, color laser image forming apparatuses which implement color images using a laser manner have also spread. The color laser image forming apparatuses typically represent the color images using four colors of toners, that is, cyan (C), magenta (M), yellow (Y), and black (K).
The color laser image forming apparatuses are divided into single path type image forming apparatuses that include four scanning units and four OPCs, and multipath type image forming apparatuses that include one scanning unit and one OPC.
In the single path type, the time required for color printing is equal to the time required for black and white printing. Therefore, the single path type is mainly used in the high-speed color laser image forming apparatuses. However, the single path type of color laser image forming apparatuses require four scanning units and four OPCs and thus become expensive. Thus, low speed color laser image forming apparatuses, which include one scanning unit and one OPC, employ the multipath type of repeatedly writing, developing, and transferring each color to form a color toner image on an intermediate transfer belt and transferring and fusing the color toner image on a paper.
On the other hand, in the color laser image forming apparatuses, image densities of yellow (Y), magenta (M), cyan (C), and black (K) may change due to several factors, such as for example, changes in environments such as temperature or humidity, changes over time in consumables including developers, and changes in development-related voltages. Color of an output image may consequently change due to changes in the image density and thus the desired color of image is not produced. Therefore, there is a need for suitably controlling the image density according to the change in the image density.
As a first method of controlling an image density in the related art, the color laser image forming apparatus autonomously forms image density patterns for four colors—C, M, Y, and K—on an intermediate transfer belt, measures reflectance using the image density (ID) sensor, and performs an electro-photography (EP) condition compensation to control an amount of toner attached on an OPC by changing a high voltage used in an EP process. In a second method, image density compensation for an intermediate gradation to change a tone reproduction curve (TRC) is handled via changes in a half-toning screen.
However, in the GDI type image forming apparatus, since a host apparatus generates binary printing data to which the half-toning screen is applied and transmits the generated binary printing data to the image forming apparatus, the image forming apparatus autonomously disables compensation for an image density of an intermediate gradation to change a TRC through changes in a half-toning screen. Therefore, the GDI type image forming apparatus only performs the EP condition compensation as the first method and thus, actively disables the compensation for the image density of the intermediate gradation. The maintenance of the image density of the intermediate gradation, reproduction of contrast characteristics and color become difficult.
In particular, when photos largely using the intermediate gradation or graphic texts are printed, color reproduction becomes difficult.